I've tried to connect 2 leds on Digital Pin0 and Digital Pin1. I know it's connected to UART RX/TX. After this connection I wasn't able to flash device - no response.But there must be some way to isolate this LEDs from RX/TX pins during programming(except putting release buttons).

So I want to have LEDs on those pins (using all pins on Arduino UNO) and be able to program board.